The present invention relates to a roller device as a paper feeder for a printer or the like, and an electronic apparatus such as printer using the roller device.
In a conventional electronic apparatus including a printing unit such as a printer, in most cases, a roller for feeding paper is arranged parallel with a motor for driving the roller and some of the gears for reducing the rotating speed of the motor. This is because the rotation of the motor needs to be transmitted to the roller after the speed is reduced, from the driving gear fixed to the motor through plural driving gears arranged in parallel thereto. As a result, the size of the entire printer becomes large.
Recently, however, as the printers and other electronic apparatuses are becoming smaller and smaller in size, the driving mechanism of cylindrical roller is required to be reduced in size. For example, has been proposed to incorporate a driving mechanism in the cylindrical roller as disclosed in Japanese Laid-open Patent No. 2-22635. This publication discloses a cylindrical roller with both ends being open, a motor accommodated at one end in this cylindrical roller, a sun gear disposed on the shaft of the motor in the cylindrical roller, planet gears engaging with the sun gear in the cylindrical roller, a cylindrical roller having a first inner tooth gear provided at the inner side of the cylindrical roller opposite to the planet gears and having a second inner tooth gear fixed to the motor and engaging the planet gears, and a drive mechanism thereof.
In this example, the second inner tooth gear is fixed to the motor. Therefore, the cylindrical roller cannot be rotated manually (if required) when feeding paper or setting paper. In other words, the first inner tooth gear of the cylindrical roller engages the second inner tooth gear through the planet gears. However, the second inner tooth gear is fixed to the motor. This motor is fixed to the fixing unit outside of the opening at one end of the cylindrical roller. The cylindrical roller cannot be turned manually and if it is attempted to turn the roller by force, the planet gears and the first and second inner tooth gears will be broken.
Meanwhile, the conventional electronic apparatus of this kind comprises, in most cases, a main body case, a sheet receiver disposed in the main body case, a roller for holding the printing sheet together with the sheet receiver, and a head for recording information on the printing sheet in the main body. Therefore, the roller is rotated while the printing sheet is being held between the roller and the sheet receiver. Thus, the printer supplies the printing sheet into the head unit, and discharges the printing sheet on which the information is recorded by the head to outside of the main body case. In this configuration, after a change of sheets, for example, it is predicted that the operation of the roller may not be secure as mentioned below.
When changing sheets, the roller needs to be separated from the sheet receiver by disconnecting the roller and a driving element such as a motor disposed outside of the roller. Therefore, in most cases hitherto, the roller and the driving element were coupled by plural gears. By disconnecting these gears, the roller can be separated from the sheet receiver.
After changing the sheets, when holding the printing sheet between the roller and sheet receiver again, the plural gears engage each other, and are coupled. The gears can engage smoothly as long as the tops and bottoms of the teeth are appropriately facing, each other. However, the tops and bottoms of the teeth are not always facing appropriately, and the gear may be deformed due to mutual collision between tops. Thus, the subsequent power transmission, that is, the roller operation may not be secure.
It is hence an object of the invention to prevent damage to the planet gears, and first and second inner tooth gears when manually rotating the cylindrical roller used in a printer or the like.
It is another object of the invention to feed the printing sheet manually by manually rotating the cylindrical roller.
It is a further object of the invention to present an electronic apparatus including a printer having a compact design.
It is still another object of the invention to present an electronic apparatus including a printer for operating the roller securely.
To achieve these objects, the roller device of the present invention includes a cylindrical roller with both ends open, a motor having a motor shaft accommodated at one end in the cylindrical roller, a sun gear disposed on the motor shaft in the cylindrical roller, and planet gears engaging the sun gear in the cylindrical roller. A bearing element has a first inner tooth gear provided at the inner side of the cylindrical roller opposite to the planet gears, and has a second inner tooth gear engaging the planet gears, and at least a support shaft of the bearing element is disposed at another end of the cylindrical roller. A bearing mechanism supports the cylindrical roller rotatably on the bearing element. At one end of the cylindrical roller, a fixing unit of the motor is provided, and the rotation of the second inner tooth gear is defined by a predetermined force.
According to this configuration, the cylindrical roller can be rotated by the rotating force of the motor, at a rotating speed and torque adequate for feeding paper. In addition, when a rotating force more than a specified value is applied to the cylindrical roller or the support shaft of the bearing element in their rotating direction, the support shaft of the bearing element rotates the cylindrical roller by way of the second inner tooth gear, planet gears, and first inner tooth gear. As a result, the printing sheet can be fed manually. Thus, the printing sheet can be fed manually without damage to the planet gears or first and second inner tooth gears. The electronic apparatus including the printer device having such roller device presents a printer having a compact design, and operates the roller securely.